Oil refineries frequency include many kilometers of pipes that require cleaning, as for example in fired heaters, where oil is heated during the refining process. One well established cleaning technique is to run a pig through the pipes under hydraulic pressure to clean the pipes. Pigs are typically polyurethane or strangulated foam cylinders or balls that are studded with scraping elements. The inventor has been a pioneer in the art of pigging, and has obtained U.S. Pat. No. 6,569,255 for a Pig and method for cleaning tubes, U.S. Pat. No. 6,391,121 for a Pig and method for cleaning tubes, U.S. Pat. No. 6,359,645 for a Pipe inspection device and method, U.S. Pat. No. 6,170,493 for a Method of cleaning a heater, U.S. Pat. No. 5,685,041 for a Pipe pig with abrasive exterior, U.S. Pat. No. 5,379,475 for a Scraper for a Pipe Pig, U.S. Pat. No. 5,358,573 for a Method of cleaning a pipe with a cylindrical pipe pig having pins in the central portion, U.S. Pat. No. 5,318,074 for a Plug for a furnace header, U.S. Pat. No. 5,265,302 for a Pipeline Pig, and U.S. Pat. No. 5,150,493 for a Pipeline Pig.
It is standard in the art of pigging for a pumping unit to include a pair of engines each driving a separate pump that is connected into a pumping circuit. Each of the pipes being pigged is connected as part of one of the pumping circuits. Flow control for the pumping circuits is provided by respective throttles on each of the engines. The engines, pumps, operator cabin, and clean and dirty water tanks are all located together on a single trailer. Such a standard pumping unit therefore can control two passes at a time, and thus clean two different pipes at a time. Operation of the pumping unit requires an operator for each engine (two people) plus a person to handle the pigs, total of three workers. In order to clean four pipes at a time, a separate pumping unit is required, and six workers. The separate pumping unit occupies scarce real estate in the refinery.